1. Field of the Invention
The present invention relates to a display apparatus and an image input apparatus used for the same, using a screen or a screen formed of a hologram. In particular, a first invention relates to a display apparatus which can suppress noise light coming into an observer""s eyes so that it is possible to improve the contrast of an image displayed on the screen, and a second invention relates to an image input apparatus which can be effectively utilized in a TV conference system, a TV telephone system, etc., and can eliminate noise components contained in an input image.
2. Description of the Related Art
First, the related arts for the first invention will be explained in detail below.
As a display apparatus which focuses an image on a screen, there is a known projector-type display apparatus which utilizes a liquid crystal as a display unit. In the display apparatus of this type, first, the light is irradiated from a predetermined direction to either a transmitting type liquid crystal or a reflecting type liquid crystal. Next, the signal light including the image formed on the liquid crystal is emitted. Further, the image to be displayed (below, a display image) contained in the signal light is focused on the screen through a focus lens. Still further, either transmitted scattered-light or reflected scattered-light of the display image, which is emitted from the screen, is visually recognized by an observer.
As another type of the projector, a CRT (Cathode Ray Tube) type is used instead of a liquid crystal type. In the CRT type projector, the display image is focused on the screen by emitting three colored beams each formed of red (R), green (G) and blue (B).
In the display apparatus utilizing a normal screen mentioned above, there is a problem in which the contrast of the displayed image deteriorates due to the incoming light, from the surroundings, on the screen in a bright environment. Accordingly, the above display apparatus can be used only in a dark environment where the incoming light is poor and the brightness is limited.
In order to solve the above problem, a first solution lies in use of an optical element according to the present invention (i.e., a reflection preventing member, a polarized optical element, a light control optical member, etc.) which is explained in detail in the description of the present invention.
Further, a second solution lies in use of a hologram as the screen (below, a hologram screen). According to the hologram screen, the characteristic of the screen can function as a scattering body for only particular light input from a particular direction due to a diffraction effect of the hologram.
That is, when the hologram which recorded the scattered light is utilized as the screen, the light is scattered for only the irradiated light (i.e., signal light) input from the particular direction, and other light input from other directions are transmitted or reflected (i.e., a regular reflection) on the screen.
As a result, almost all light input from the surroundings is not scattered on the screen. Accordingly, it is possible to solve a problem in which the brightness at the background of the screen is increased, and the contrast of the displayed image can be improved. This conventional art has been disclosed, for example, in the Japanese Unexamined Patent Publication (Kokai) No. 5-333435.
Further, in addition to the above structure using the hologram screen, there is a method in which an external light absorbing member (for example, black paint, etc.) which absorbs the external light is provided inside of the hologram screen in order to absorb the external light. This art has been disclosed, for example, in the Japanese Unexamined Patent Publication (Kokai) No. 5-88020.
In this art, however, there is another problem as explained below. That is, when the strong external light, such as sunlight or the light of a lamp, which is input from the direction opposite to the signal light, is input on the hologram screen, the diffracted light is reflected on the rear side of the hologram screen, and the reflected light is directed to the observer. As a result, the contrast of the image becomes worse and the observer is very hard to observe the displayed image.
As a solution for the above problem, the following method has been proposed. That is, a reflection preventing member is provided to the rear side of the screen, and a polarized optical element is provided on the observer""s side of the hologram screen.
In the display apparatus using the hologram screen, as explained above, when strong external light, such as sunlight or the light of the lamp, is input to the hologram screen, it is possible to reduce noise light caused by the scattering or diffraction on the hologram screen.
There are problems, however, in the above explained conventional arts as briefly explained below. That is, in the conventional hologram screen, regardless of the diffraction, there is the difference in refractive index on the boundary surface between the external air and the structural member of the hologram screen in the observer""s side and in the rear side, and, as a result, reflection occurs in the boundary surface. As a result, the background at the observer""s side overlaps with the image displayed on the hologram screen so that there is a problem in which it is difficult to see the image due to deterioration of the contrast of the image.
Further, since the hologram screen has a light-transmitting characteristic, and since the observer can see the rear side of the image (i.e., a rear side of the hologram screen), when there is internal light, such as the light from a room lamp, on the rear side of the image, the internal light is overlapped with the image so that the contrast of the image is deteriorated and the observer is difficult to see the displayed image. The above two problems are explained in detail with reference to FIGS. 11 and 12 below.
Next, the related arts for the second invention will be explained in detail below.
For example, when taking a picture of a speaker through a camera in a TV conference system, a TV telephone system, a prompter system, etc., the viewline of the speaker is usually directed to a display unit of the system, and is not directed to the camera (i.e., an image input unit). Accordingly, in actual use of the TV conference system or the TV telephone system, there is a problem in which a feeling of disorder occurs between speakers since the viewline of one speaker does not meet that of another speaker through the camera.
As one solution of this problem, there is a known art disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 6-30406. According to this document, in order for the viewlines between speakers to meet, the signal light in which the information to be displayed is recorded therein is irradiated to a screen which has the function of transmitting or scattering the light in accordance with the incident angle of the light, the speaker""s image is displayed on the screen, and the image of the speaker (i.e., the observer who watches the display unit) is captured by the image input unit (i.e., a camera) through the screen.
As another solution, there is another known art disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 9-168141. According to this document, the signal light in which the information to be displayed is recorded therein is irradiated to the hologram screen (i.e., as mentioned above, the hologram is used as the screen), another speaker is displayed on the hologram screen, and the image of the speaker (i.e., the observer who watches the display unit) is captured by the image input unit (i.e., a camera) through the hologram screen. There are, however, subjects to be solved in these conventional arts as explained in detail with reference to FIGS. 29 to 31 below.
The object of the first invention is to provide a display apparatus which can suppress the first noise light caused by the background on the observer""s side and the second noise light caused by the background on the rear side of the hologram screen so that it is possible to increase the contrast of the normal image to be displayed on the screen or the hologram screen.
Further, the object of the second invention is to provide an image input apparatus used for the display apparatus defined in the first embodiment, which can eliminate noise components contained in the image signal and can provide a desirable clear image.
In the following descriptions, a light-transmitting type screen (or a hologram screen) is provided between an irradiating unit and an observer. On the other hand, a light-reflecting type screen (or a hologram screen) is provided to one side of the irradiating unit and the observer, as shown in the drawings.
In accordance with one aspect of the first invention, there is provided a display apparatus including: an irradiating unit for generating signal light which records information to be displayed; a light-transmitting type screen (or a hologram screen) which transmits the signal light input by the irradiating unit to an observer; and a reflection preventing member provided to either both sides, i.e., the observer""s side and the rear side, or any one side, of the light-transmitting type screen (or the hologram screen).
The above reflection preventing member can reduce the reflection from the screen or hologram screen at the background of the observer""s side, and the intensity of noise light directed to the observer can be considerably reduced so that it is possible to increase the contrast of the image.
In accordance with another aspect of the first invention, there is provided a display apparatus including: an irradiating unit for generating signal light which records information to be displayed, and the signal light being linear polarized light; a light-transmitting type screen (or the hologram screen) which transmits the signal light input by the irradiating unit to an observer; and a polarized optical element provided to the rear side of the light-transmitting type screen (or the hologram screen) and formed so as to selectively transmit the linear polarized light.
The polarized optical element can reduce the second noise from the background of the rear side to approximately one sixth or one seventh. Further, since the signal light (i.e., a linear polarized light) is orthogonally crossed to an absorption axis of the polalized optical element, almost all signal light from the irradiating unit can pass through the hologram screen.
In accordance with still another aspect of the first invention, there is provided a display apparatus including: an irradiating unit for generating signal light which recorded information to be displayed, and the signal light being linear polarized light; a light-transmitting type screen (or the hologram screen) which transmits the signal light input by the irradiating unit to an observer; a polarized optical element provided to the rear side of the light-transmitting type screen (or the hologram screen) and formed so as to selectively transmit the linear polarized light; and a reflection preventing member provided to the outside of the polarized optical element.
The polarized optical element can reduce not only the second noise from the background on the rear side, but also a first noise in which the background on the observer""s side is reflected at the rear of the hologram screen. Accordingly, it is possible to increase the contrast of the image for a first noise.
In accordance with still another aspect of the first invention, there is provided a display apparatus including: an irradiating unit for generating signal light which records information to be displayed, the signal light being linear polarized light; a light-transmitting type screen (or the hologram screen) which transmits the signal light input by the irradiating unit to an observer; a reflection preventing member provided to the observer""s side of the light-transmitting type screen (or the hologram screen); and a polarized optical element provided to the rear side of the light-transmitting type screen (or the hologram screen) and formed so as to selectively transmit the linear polarized light.
In accordance with still another aspect of the first invention, there is provided a display apparatus including: an irradiating unit for generating signal light which records information to be displayed, and the signal light being linear polarized light; a light-transmitting type screen (or the hologram screen) which transmits the signal light input by the irradiating unit to an observer; a reflection preventing member provided to the observer""s side of the light-transmitting type screen (or the hologram screen); a polarized optical element provided to the rear side of the light-transmitting type screen (or the hologram screen) and formed so as to selectively transmit the linear polarized light; and another reflection preventing member provided to the outside of the polarized optical element.
In accordance with still another aspect of the first invention, there is provided a display apparatus including: an irradiating unit for generating signal light which records information to be displayed; a light-reflecting type screen (or the hologram screen) which reflects the signal light input by the irradiating unit to an observer; and a reflection preventing member provided to either both sides, i.e., the observer""s side and the rear side, or any one side, of the light-reflecting type screen (or the hologram screen).
In accordance with still another aspect of the first invention, there is provided a display apparatus including: an irradiating unit for generating signal light which records information to be displayed; a light-reflecting type screen (or the hologram screen) which reflects the signal light input by the irradiating unit to an observer; and a half-transparent or non-transparent optical member, or a polarized optical member provided to the rear side of the light-reflecting screen (or the hologram screen).
In accordance with still another aspect of the first invention, there is provided a display apparatus including: an irradiating unit for generating signal light which records information to be displayed; a light-reflecting type screen (or the hologram screen) which reflects the signal light input by the irradiating unit to an observer; a reflection preventing member provided to the observer""s side of the light-reflecting type screen (or the hologram screen); and a half-transparent or not-transparent optical member, or a polarized optical member provided to rear side of the light-reflecting type screen (or the hologram screen).
In a preferred embodiment, an image contrast of the display apparatus is 2 or more.
In another preferred embodiment, a luminous reflection factor of the reflection preventing member is 2.5(%) or less.
In still another preferred embodiment, a light-transmittance factor of the polarized optical element is 65(%) or less.
In still another preferred embodiment, the reflection preventing members provided to both sides, i.e., the observer""s side and the rear side, of the light-transmitting type screen (or the hologram screen) or the light-reflecting type screen (or the hologram screen) are lustrous.
In still another preferred embodiment, the reflection preventing members provided to both sides, i.e., the observer""s side and the rear side, of the light-transmitting type screen (or the hologram screen) or the light-reflecting type screen (or the hologram screen) are a non-glare type optical members.
In the present invention, the term xe2x80x9clustrousxe2x80x9d means a low reflection factor in which a thin film is formed on the surface so as to reduce the reflection factor based on an interference effect. Further, the term xe2x80x9cnon-glarexe2x80x9d means low scattered light by scattering the incident light on an uneven surface.
In still another preferred embodiment, the reflection preventing members provided to both sides, i.e., the observer""s side and the rear side, of the light-transmitting type screen (or the hologram screen) or the light-reflecting type screen (or the hologram screen) are a lustrous non-glare type reflection preventing member having both a lustrous-type reflection preventing characteristic and a non-glare type reflection preventing characteristic.
In still another preferred embodiment, a light-control type optical member is provided between the reflection preventing member at the observer""s side and the light-transmitting type screen (or the hologram screen) or the light-reflecting type screen (or the hologram screen).
In accordance with one aspect of the second invention, there is provided an image input apparatus used in a display apparatus including: an irradiating unit for generating signal light which records information to be displayed; a display unit for projecting the signal light irradiated by the irradiating unit; an image input unit for inputting an desired object which exists another side of the display unit, through the display unit from one side of the display unit, as an image signal; and a noise eliminating unit for eliminating at least a some of the image component except for the desired object.
The noise eliminating unit can considerably reduce noise components contained in the image signals input to the image input unit so that it is possible to provide good appearance of the image on the display apparatus.
In a preferred embodiment, the noise eliminating unit is directly provided to the display unit.
In another preferred embodiment, the noise eliminating unit is a reflection preventing member which is provided to either both sides, i.e., the one side and another side, or any one side of the display unit.
In still another preferred embodiment, a reflection factor of the reflection preventing member is 2.5(%) or less.
In still another preferred embodiment, the noise eliminating unit is at least any one kind of a polarized optical member, a light-control type optical member and a colored optical member.
In still another preferred embodiment, the noise eliminating unit is an image processing circuit for eliminating noise signals input by the image input unit.
In still another preferred embodiment, the image processing circuit eliminates the noise signals of the image from the information to be displayed from the irradiating unit and the input image signal from the image input unit.
In still another preferred embodiment, the image processing circuit inputs noise signals, which are observed from a side of the image input unit, to the image input unit when there are no object at another side of the display unit and no irradiation light irradiated from the irradiating unit to the display unit; after the noise signals are recorded, when the desired image which exist another side of the display unit, the recorded noise signals are eliminated by the image signal input by the image input unit.
In still another preferred embodiment, the noise eliminating unit has both noise eliminating unit, which is directly provided to the display unit, and the image processing circuit for eliminating noise signals from the image signal input by the image input unit.
In still another preferred embodiment, the noise eliminating unit has at least any one kind of a reflection preventing member, a polarized optical member, a light-control type optical member and a colored optical member, these provided to the display unit; and an image processing circuit for eliminating noise signals from the image signal input by the image input unit.
In still another preferred embodiment, the display unit is a light-transmitting type screen or a light-reflecting type screen.
In still another preferred embodiment, the display unit is a light-transmitting type hologram screen or a light-reflecting type hologram screen.
In still another preferred embodiment, the irradiating unit, the display unit and the image input unit are provided integratedly within a box, and brightness at an inside of the box is lower than the brightness at an outside of the box.
In still another preferred embodiment, the image input apparatus further comprises, an amount of light detecting unit for detecting the amount of light at peripheral portions of the display unit, and an irradiation intensity adjusting unit for changing the irradiation intensity of the irradiation unit.